1. Field of the Invention
The present invention relates to an apparatus for manufacturing a semiconductor device, and more specifically to a plasma CVD (chemical vapor deposition) apparatus for manufacturing a semiconductor device.
2. Description of Related Art
Conventional plasma CVD apparatuses have been fundamentally so constituted that a semiconductor wafer is located and supported on a semiconductor wafer holder and lower electrode connected to a common ground terminal, and an upper electrode connected to a RF (radio frequency) voltage supply is located separately from the semiconductor wafer but opposite to the semiconductor wafer. The RF voltage causes a plasma discharge between the lower and upper electrodes, so that a plasma region is created on a surface of the semiconductor wafer. In this condition, a reacting gas is introduced to the plasma region, so that the reacting gas is ionized, and a film is deposited or grown the semiconductor wafer. In this manner, the semiconductor wafer is used as a semiconductor substrate in a process of manufacturing a semiconductor device, and various necessary films can be deposited on the semiconductor substrate.
In the above mentioned plasma CVD process, electric charges created by the plasma am accumulated in a deposited film, and therefore, characteristics of a finished semiconductor device are influenced by the electric charges accumulated in the deposited film. In other words, the characteristics of the finished semiconductor device have often deviated from expected characteristics.